Breeding Success for Recently Released Endangered Coho in Redwood Creek

Adult female hatchery-reaised coho being released into Redwood Creek. Notice the bright pink tag at the base of the coho's dorsal fin. These colored tags allow biologists monitoring spawning activity in the creek to distinguish between wild and hatchery fish. NPS / Gabriela Dunn

February 2018 - Last month we reported on the release of 188 hatchery-raised adult coho salmon (Oncorhynchus kisutch) into Redwood Creek in an attempt to increase this population’s dwindling numbers. Since the release, monitoring crews have been surveying the creek weekly to count the number of coho salmon nesting sites, or redds, and document their locations along the stream.

Biologists have found at least 35 coho redds that they believe were created by the released fish due to the presence of hatchery adults at or near the nesting site at the time of the observation. In total 193 live adult coho, 23 coho carcasses, and 55 coho redds were counted. Most of both the live fish and carcasses were those that were reared in the hatchery and released in January.

Even with the dry winter, some of these fish were seen over three miles upstream of the closest release site. With redds so spread out along the stream, biologists hope that the young fry that hatch from them will have better chances of surviving the challenges of spring. High flows and competition with other fish, including other coho, are among the first threats that fry face. Once the eggs hatch and the coho fry emerge out of the gravel, they will spend the next year in Redwood Creek before heading out to sea. Based on the number of redds documented this winter, biologists anticipate that Redwood Creek will have over 10,000 juvenile coho within its mainstem this summer—the highest number in ten years!

Contact Michael Reichmuth for more information.

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